This invention relates to electrical power generation using mirror photon concentrators, specifically in advantageous size ranges and methods of making the devices. This invention also describes the forming of a plurality of small mirrors.
Prior attempts to make photovoltaic devices which produce electrical power from high intensities of photons have had problems with economic success. That has been due to a number of disadvantages.
Large amounts of expensive semiconductor material are typically required to manufacture state-of-the-art photovoltaic devices to convert photons to electricity. Those materials are expensive and thus lead to expensive photovoltaic devices.
The manufacturing methods used in the past had a large number of mechanical steps and were inefficient, such as forming classic crystalline silicon cells. In that process photovoltaic arrays were formed from sliced wafers, from a silicon crystal boole and in subsequent processing steps. In that process approximately 80% of the semiconductor was turned into dust and was recycled, and there were many mechanical operations. The increased number of mechanical operations needed to manufacture something typically drives up the cost of the product and reduces the reliability.
Locating an aperture and a semiconductor on the smooth back plane of an assembly with lasers limits the methods and materials that can be used. Many promising semiconductor materials are not amenable to processing by laser heating. Short thermal cycles, contact with surrounding materials, or extreme temperature gradients during semiconductor crystallization could present problems in obtaining optimum electrical properties.
The laser power needed to form the solar cells rises as the cells become smaller because of the increased cooling efficiency as the dimensions get smaller.
Suitable lens materials may not have the mechanical properties needed for the tasks compared to thin film mirrors, such as in processes or applications where the array would ideally be rolled up. Most inorganic optical materials are brittle and many plastic materials will optically degrade with long exposure to UV light.
In a lens-concentrating photovoltaic system components are mechanically assembled. Parts of the structural system are fresnel lenses and frames. That adds significant volume and mass to the system.
Thin single-layer silicon solar cells have been reported to be efficient because carrier diffusion length is an order of magnitude longer than the cell is thick, providing high open circuit voltages.
Solar cells formed with spherical silicon and connections to the silicon spheres provide cost advantages over slices of a single crystal or vapor-deposited semiconductors, because semiconductor spheres can be formed without interaction with the surrounding materials.
Fault tolerance in typical thin-film photovoltaic cells is poor; reduced performance and even catastrophic cascade failures occur with faults. State-of-the-art photovoltaic cells require metal conductor connections that are significant parts of the mass. They are often formed in separate steps. Shorting liability results from the amount of metal used to keep the resistance losses low. Large metal conductors allow large arcs to form and thus damage large areas around the arc, or even weld sufficient metal to short-circuit the entire photovoltaic array.
Needs exist for improved photon collectors and photovoltaic cells.